This section provides information helpful in understanding the invention but that is not necessarily prior art.
Ionomeric resins or ionomers have found use in golf balls. Ionomers are generally ionic copolymers of an olefin (such as ethylene) and a metal of an ethylenically unsaturated carboxylic acid (such as acrylic acid, methacrylic acid, or maleic acid). Metal cations such as sodium or zinc are used to neutralize some portion of the acidic groups in the copolymer resulting in a thermoplastic elastomer exhibiting enhanced properties such as durability for golf ball covers. Available soft ionomer materials, though not as durable or quite as soft as polyurethanes, still have the capability of generating high spin and soft feel.
Ionomers have also found use as a material for cores or other layers between a core and cover (e.g., an outer core layer or mantle layer) of golf balls. Higher hardness ionomers are utilized underneath a soft cover as a mantle layer of the golf ball. The soft-over-hard construction allows for spin separation from the driver to the wedge, or low spin off the driver and high spin off the wedge. In other words, the hard ionomer mantle allows for lower spin off the tee using a driver where a larger portion of the ball is compressed when hit. On higher-angled clubs, such as wedges, the golf ball is not compressed as much as off the tee, and the softer outer cover results in high spin for shots into the green. Modified ionomers with a high degree of neutralization maybe used as parts of the core or inner layers of the golf ball due to their high resilience. Golf balls in which the core or other inner layers are made from materials with high coefficients of restitution (elasticity) generally provide longer distance. Most professional golfers and good amateur golfers desire a golf ball that provides distance when hit off a driver, control and stopping ability on full iron shots as well as high spin on short “touch and feel” shots.